The pulvinar is the largest nucleus in the primate thalamus and is considered a higher-order thalamic nucleus because it forms input-output loops almost exclusively with the cortex. From an anatomical perspective, the pulvinar is ideally positioned to regulate the transmission of information to the cortex and between cortical areas to influence perceptual and cognitive processes. However, experimental evidence in support of such a functional role has been sparse. The most compelling evidence for the pulvinar playing an important role in visual perception and cognition has come from lesion studies in humans and monkeys. These studies point to the critical involvement of the pulvinar in a number of fundamental cognitive functions, including orienting responses and the exploration of visual space, feature binding, and the filtering of unwanted information. The underlying neural correlates of these cognitive operations in the pulvinar are largely unclear. The proposed project aims at defining the role of the pulvinar in visual attention. The central hypothesis is that the pulvinar is an integral subcortical part of a large-scale network mediating the selection of behaviorally relevant information and that it operates by co-ordinating activity in cortical areas. By using an integrated multi-modal methods approach that includes functional magnetic resonance imaging (fMRI), diffusion tensor imaging (DTI) and behavioral measures in humans and monkeys, and invasive electrophysiology in monkeys we will probe these ideas by pursuing two main aims: (i) to characterize the temporal dynamics of pulvino-cortical interactions by simultaneously recording from interconnected areas in macaque pulvinar and cortex in animals trained to perform a spatial attention task and (ii) to characterize the large-scale functional organization of the human pulvinar, which is largely uncharted brain territory, and its attention functions relative to cortical attention networks. The significance of the proposed research is that it will contribute to a better understanding of the pulvinar's role in a fundamental cognitive operation, selective attention, the impairment of which has devastating consequences on human health. Attentional deficits are frequently observed in neurological diseases (e.g. after stroke) leading to visuo-spatial neglect, an impairment in directing attention to contralesional visual space, as well as in psychiatric diseases (e.g. schizophrenia). Our proposed studies also aim at defining the pulvinar's role in integrating information from different cortical areas according to the behavioral context, which will help solve one of the deep mysteries in cognitive neuroscience, that is, to understand the functions of thalamo-cortical interactions in perception and cognition. ! PUBLIC HEALTH RELEVANCE: The proposed research is relevant to public health because it aims at advancing our understanding of neural mechanisms underlying selective attention, which is one of the most fundamental cognitive abilities for guiding behavior. This becomes strikingly clear when attentional selection mechanisms fail, such as in individuals afflicted with ADHD, visuo-spatial hemineglect that is often observed following stroke, and schizophrenia. Progress in understanding the basic mechanisms of selective attention is a first necessary step in developing effective treatment strategies for attentional deficits.